1. Field of the Invention
The present invention relates to a touch panel structure and, more particularly, to a high-accuracy single-layer capacitive touch panel device with one side for connection.
2. Description of Related Art
Currently, capacitive touch panels are in widespread use, and are primarily applied in consumer electronic apparatuses, such as PDA, palmtop computer, electronic dictionary, mobile phone, web pad, electronic book, tablet PC, digital camera, self-ordering system, stocktaking machine, POS cash register, credit card POS signature machine, and medical monitoring system.
On the other hand, a resistive touch panel is formed by overlapping an upper ITO (Indium Tin Oxide) conductive layer and a lower ITO conductive layer. The pressure applied to the touch panel will cause the electrodes of the upper layer to conduct with the electrodes of the lower layer. A controller calculates the position of the touch point by detecting the voltage variation of the touch panel. When a user touches a certain point on the screen, a current is caused due to the conduction so as to generate an operation, and a processor calculates the position of the operated point, while a driver translates such an operation into the language that the system can understand.
For the single-layer capacitive touch panel device, it is arranged to connect the two sides of the conductive layer to a detection circuit for measuring the current and voltage variations on the conductive layer. Such skills can be found in, for example, U.S. Pat. No. 6,961,049 granted to Mulligan, et al. for a “Capacitive touch sensor architecture with unique sensor bar addressing”, and U.S. Pat. No. 7,735,383 granted to Dattalo, et al. for a “Balanced resistance capacitive sensing apparatus”. However, this arrangement needs to dispose the connection wires at two sides of the substrate, resulting in negatively influencing the overall appearance of the touch panel, badly affecting the product design, and erroneously determining the touched point due to the connection wires at the sides.
To solve the aforementioned problem, one solution is to dispose the connection wires at one side of the substrate. FIG. 1 is a schematic diagram of a prior single-layer capacitive touch panel device with one side for connection and its touch detection circuit. As shown in FIG. 1, the prior single-layer capacitive touch panel device 1 includes a substrate 10, a plurality of conductive lines 101-110, and a touch detection circuit 11. Each of the plurality of conductive lines 101-110 is of a bar shape and arranged on the surface of substrate 10 in parallel with each other, and is electrically connected to the touch detection circuit 11 through a connection wire 19. The plurality of conductive lines 101-110 are extended from the first side 10a to the second side 10b of the substrate 10. Each conductive line 101-110 has a connection part 101b-110b close to the second side 10b. The touch detection circuit 11 is electrically connected to the connection part 101b-110b of the conductive lines 101-110 through the connection wires 19, so as to detect the variations of electrical characteristic of the plurality of conductive lines 101-110, thereby determining at least one touch point A on the substrate 10.
The touch point detection of FIG. 1 is performed by detecting the capacitance variations of the plurality of conductive lines 101-110 to determine the Y-direction coordinate of the touch point A (e.g., the conductive line 108), and then detecting the resistance variation of the conductive line 108, so as to determine the X-direction coordinate of the touch point A. Such a detection method encounters a dilemma. When the width of the conductive line 101-110 in increased, the spacing between two conductive lines 101-110 is decreased to facilitate in detecting the capacitance variations of the plurality of conductive lines 101-110. However, because the width of the conductive line 101110 is increased, the resistance of each of the conductive lines 101-110 becomes smaller, resulting in a difficulty in detecting the resistance variations of the conductive lines. When the width of the conductive line 101-110 is decreased, the resistance of each conductive line 101-110 is increased to facilitate in detecting the resistance variations of the conductive lines, but the spacing between two conductive lines 101-110 is increased and thus the capacitance thereof becomes smaller, which is disadvantageous in detecting the capacitance variations of the conductive lines 101-110.
Therefore, it desired for the aforementioned single-layer capacitive touch panel device structure to be improved.